Select all the correct answers.
Which equations represent precipitation reactions?
[tex]$Na _2 S+ FeBr _2 \rightarrow 2 NaBr + FeS$[/tex]
[tex]$MgSO _4+ CaCl _2 \rightarrow MgCl _2+ CaSO _4$[/tex]
[tex]$LiOH + NH _4 I \rightarrow Lil + NH _4 OH$[/tex]
[tex]$2 NaCl + K _2 S \rightarrow Na _2 S+2 KCl$[/tex]
[tex]$AgNO _3+ NaCl \rightarrow AgCl + NaNO _3$[/tex]
Answer (1)
Identify precipitation reactions by checking for the formation of an insoluble solid (precipitate).
N a 2 S + F e B r 2 → 2 N a B r + F e S : F e S is insoluble, so it's a precipitation reaction.
M g S O 4 + C a C l 2 → M g C l 2 + C a S O 4 : C a S O 4 is considered insoluble, so it's a precipitation reaction.
A g N O 3 + N a Cl → A g Cl + N a N O 3 : A g Cl is insoluble, so it's a precipitation reaction.
The correct answers are: N a 2 S + F e B r 2 → 2 N a B r + F e S , M g S O 4 + C a C l 2 → M g C l 2 + C a S O 4 , and A g N O 3 + N a Cl → A g Cl + N a N O 3 . N a 2 S + F e B r 2 → 2 N a B r + F e S ; M g S O 4 + C a C l 2 → M g C l 2 + C a S O 4 ; A g N O 3 + N a Cl → A g Cl + N a N O 3
Explanation
Identifying Precipitation Reactions We need to identify which of the given reactions are precipitation reactions. A precipitation reaction occurs when two aqueous solutions react to form an insoluble solid (precipitate). We will analyze each reaction to determine if a precipitate is formed.
Analyzing Reaction 1
N a 2 S + F e B r 2 → 2 N a B r + F e S : Sodium sulfide ( N a 2 S ) and iron(II) bromide ( F e B r 2 ) react to form sodium bromide ( N a B r ) and iron(II) sulfide ( F e S ). F e S is insoluble in water, so this is a precipitation reaction.
Analyzing Reaction 2
M g S O 4 + C a C l 2 → M g C l 2 + C a S O 4 : Magnesium sulfate ( M g S O 4 ) and calcium chloride ( C a C l 2 ) react to form magnesium chloride ( M g C l 2 ) and calcium sulfate ( C a S O 4 ). C a S O 4 is slightly soluble, but for the purpose of this problem, we will consider it insoluble, so this is a precipitation reaction.
Analyzing Reaction 3
L i O H + N H 4 I → L i I + N H 4 O H : Lithium hydroxide ( L i O H ) and ammonium iodide ( N H 4 I ) react to form lithium iodide ( L i I ) and ammonium hydroxide ( N H 4 O H ). All of these compounds are soluble, so this is not a precipitation reaction.
Analyzing Reaction 4
2 N a Cl + K 2 S → N a 2 S + 2 K Cl : Sodium chloride ( N a Cl ) and potassium sulfide ( K 2 S ) react to form sodium sulfide ( N a 2 S ) and potassium chloride ( K Cl ). All of these compounds are soluble, so this is not a precipitation reaction.
Analyzing Reaction 5
A g N O 3 + N a Cl → A g Cl + N a N O 3 : Silver nitrate ( A g N O 3 ) and sodium chloride ( N a Cl ) react to form silver chloride ( A g Cl ) and sodium nitrate ( N a N O 3 ). A g Cl is insoluble in water, so this is a precipitation reaction.
Final Answer Therefore, the equations that represent precipitation reactions are: N a 2 S + F e B r 2 → 2 N a B r + F e S M g S O 4 + C a C l 2 → M g C l 2 + C a S O 4 A g N O 3 + N a Cl → A g Cl + N a N O 3
Examples
Precipitation reactions are essential in water treatment. For example, adding iron(III) chloride to water causes iron(III) hydroxide to precipitate, which can then be filtered out, removing impurities from the water. This process is crucial for providing clean and safe drinking water. Similarly, in industrial processes, precipitation reactions are used to recover valuable metals from solutions or to remove unwanted contaminants.
